When cities sprawl and highways slice through natural habitats, the result can be a tragic tally of road‑kill and fragmented ecosystems. Fortunately, engineers and conservationists have turned the problem into an opportunity, designing safe passages that let wildlife move freely again. Below you’ll find 10 fascinating facts about wildlife crossings—each one a clever solution that blends infrastructure with ecology.
10 Fascinating Facts About Wildlife Crossings
10 Eco‑Ducts
Across Europe, nations such as the Netherlands, Switzerland, Germany, and France have been pioneering wildlife overpasses and underpasses for decades. In the Netherlands these structures are known as eco‑ducts, and the country already boasts roughly 600 of them. Built on protected terrain, eco‑ducts are off‑limits to mining, drilling, or hunting, ensuring they remain safe sanctuaries for passing fauna. Dutch planners have ambitious expansion plans, aiming to add even more eco‑ducts to their network.
Innovation isn’t limited to Europe. Other regions are getting creative, too. South Korea, for example, hosted the Yangjaegogae Eco‑bridge Design Competition in Seoul, where designers submitted concepts that mimic the sloping mountains they connect. The winning entry gracefully arches over a bustling eight‑lane highway, giving countless creatures a secure route across the divide.
9 Not a New Invention
Long before modern highways, the 17th‑century French already tackled passage problems by bundling branches into fish ladders—essentially staircases for fish navigating steep waterways. These ladders, constructed from rocks, lumber, or logs, let fish bypass obstacles and reach spawning grounds, food sources, and mates. Though the image of fish climbing a ladder sounds whimsical, the ladders are vital for their life cycles.
In North America, Canadian lumber‑mill owner Richard McFarland patented a fishway in 1837 to help fish evade his dam. His design was the first of its kind to receive a patent, and today fish ladders are commonplace, especially in turbulent rivers where upstream migration would otherwise be impossible.
8 Biodiversity
Wildlife crossings have become a cornerstone of modern conservation, boosting animal numbers and enriching biodiversity—the variety of life that fuels ecosystem resilience. By reconnecting habitats, these corridors restore the flow of genetic material, food, and shelter, preventing the cascade of problems that follow population declines.
Japan illustrates this principle with its “Turtle Tunnels,” subterranean passages beneath train tracks that safeguard turtles from rail traffic. A similar tunnel in Massachusetts, built under Route 44, reunites two spotted‑turtle populations split by the road, allowing fresh genetic exchange and enhancing the turtles’ ability to adapt to environmental changes.
7 From Mice to Grizzlies
Canada’s Banff National Park showcases a comprehensive network of 44 wildlife passages—six overpasses and 38 underpasses—installed since a 1978 road‑improvement project. The Trans‑Canada Highway, which carries nearly 18,000 vehicles daily, is now threaded with these structures, permitting a broad spectrum of species to cross safely.
Camera monitoring reveals distinct preferences: grizzlies, deer, and moose favor the open‑air overpasses, while cougars tend toward darker underpasses that provide concealment. Smaller critters, from voles to mice, make use of the myriad culverts peppered throughout the park, demonstrating that size‑inclusive design benefits the entire animal community.
6 Christmas Crabs
Among the world’s most iconic crossings is the crab bridge on Australia’s Christmas Island. Home to about 45 million vivid red crabs on a mere 52‑square‑mile island, the species faces a perilous road that bisects its annual migration route. To ease this, locals erected a 16‑foot bridge over the main thoroughfare, allowing the crabs to safely travel from forest to sea during spawning season.
The bridge has become a tourist magnet, drawing visitors eager to witness the spectacular sight of millions of crimson crabs marching in unison. While additional underpasses also aid the crabs, the elevated bridge remains the most visually striking solution.
5 Avoiding A Cat‑astrophe
Florida’s landscape is dotted with more than twenty wildlife crossings designed to protect the endangered Florida panther. Once teetering on the brink of extinction in the 1970s, the panther’s numbers have rebounded thanks in part to these underpasses, which mitigate the deadly threat of vehicle collisions.
Even with these corridors, the panther remains vulnerable. The animal’s survival hinges on continuous, vegetated habitats that allow it to roam and hunt. By cloaking the crossings in native plants and flowers, Florida provides panthers with a seamless extension of their natural range, bolstering population recovery—though, sadly, they won’t be helping the Carolina Panthers on the football field!
4 No Monkeying Around
Costa Rica’s “monkey bridges” were installed to keep primates from using dangerous electrical wires to swing across the forest canopy. Constructed from sturdy rope, these overhead walkways give monkeys a safe, reliable route between trees, dramatically reducing electrocution incidents.
Surprisingly, the bridges have attracted a whole suite of other residents—sloths, anteaters, even porcupines—who now cross with their young safely in tow. Watching a troop of monkeys traverse a rope bridge high above the rainforest is a reminder that simple engineering can make a big difference for many species.
3 Over the Down Under Bridge
Australia’s wildlife bridges and tunnels were once thought unsuitable for koalas, but ecologist Darryl Jones of Griffith University proved otherwise. Within three weeks of a 2016 installation, koalas were confidently using the structures, demonstrating that even the most arboreal creatures can adapt to engineered pathways.
These passages are often lined with native vegetation, making them appear as natural extensions of the landscape. While originally built for squirrel gliders, the same bridges now host wrens, finches, and a host of other feathered visitors, illustrating the versatility of well‑designed wildlife corridors.
2 Keeping It Natural
Since the 1990s, the United States has erected thousands of wildlife crossings, ranging from subterranean tunnels to expansive bridges that accommodate elk, moose, and countless other species. These corridors not only cut down road‑kill incidents but also reconnect fragmented habitats, allowing animals to move freely across the landscape.
Modern designs emphasize ecological authenticity: engineers plant native trees and shrubs on bridge decks, creating green corridors that blend seamlessly with surrounding environments. Paired with strategic highway fencing, these “green bridges” funnel wildlife toward safe crossing points, dramatically improving passage efficiency.
1 Going Bigger
The world’s largest wildlife overpass is currently rising in California, just northwest of Los Angeles. Named the Wallis Annenberg Wildlife Crossing, this ten‑lane span over the 101 freeway will serve pumas, deer, coyotes, rabbits, squirrels, lizards, and many other species, while also hosting a pedestrian and bike path for people.
Construction began in earnest to address the alarming decline of mountain lions in the Santa Monica Mountains. The freeway had isolated lion populations, leading to genetic bottlenecks and a drop in numbers. Earlier attempts to provide an underpass proved fatal for several lions, underscoring the need for a more effective solution.
When completed, the overpass will reconnect the Santa Monica range with the Simi Valley mountains, allowing lions and other wildlife to safely traverse the corridor, exchange genes, and thrive. As a Southern California resident, I can’t wait to stroll across this marvel and watch nature reclaim its pathways.